TfL announced that the area covered by the scheme will be expanded, but the timing of the extension depends on how much TfL's budget suffers on October 20th when the government announces its spending review.

Setting up the bike hire scheme is set to cost £140m over six years. TfL expect it will cover its operating costs within two to three years and will then be able to contribute to its implementation costs. Charlie Lloyd from the London Cycling Campaign (LCC) said:

"It is very likely they will make some kind of profit on this, and you have to bear in mind that London Transport makes a loss on every single bus and tube journey. So this is a good value transport investment."

As expected, most of the scheme's users make their journeys under 30 minutes because this keeps the price they pay down to £1 a day. This lowers profits but, as David Brown, managing director of surface transport for TfL, pointed out, it draws people away from the heavily subsidised and over-crowded bus and tube network – which was one of TfL's aims.

Lloyd said: "We think it is a success story, most of the problems are to do with its success really." He was referring to the lengthy grilling the transport committee gave Weimar about over-charging problems and long waits for help on expensive phone lines. Weimar's response was to apologise and say that these were teething problems that had now been fixed.

Committee member James Cleverly asked when the scheme would work with the Oyster card. Brown from TfL was adamant that this would never happen. He said this was down to the technology behind the Oyster card and that it would be too expensive. "And besides, they are moving on to contactless [payments] anyway, so we would have spent all that money and we would be behind the curve."

There was a row among the committee about helmets, as casual bike hire riders are unlikely to use one. Seven bike hire riders have been injured so far, and two needed headscans, but these were precautionary and all the injuries were minor, Brown told the committee. Only the chair, Valerie Shawcross, stuck up for the benefits of helmets. Other members accused her of governing the committee according to personal prejudice. Oliver Schick from LCC said there was no evidence that wearing a helmet had safety benefits. The chair said that there was no feasible way that they too could be hired, but eventually insisted that they should be strongly advocated in all signage and marketing as advising people to wear them is national policy.

The scheme will be expanded with new areas bolted on the central zone as finances permit. Top of the list are Canary Wharf, Camden and Tower Hamlets, although others are being considered.

Brown said the scheme could never deal with commuters from railway hubs like Victoria or Waterloo. "We could never cope with that level of demand. We would need docking stations the size of five football pitches."

He said it was crucial to find different routes that the bikes could be used for so that the operators were able to manage the redistribution. Canary Wharf and Camden made it to the top of the list because they have a mixture of attractions and that users would move the bikes around between work, leisure, home, and transport hubs – so that Serco has less redistribution to do.

Andrew Boff asked Brown if there was a logical maximum size for the scheme. To which Brown said: "The inhibitor is cost and not demand. The Paris Velib scheme is still growing and they've got 20,000 bikes."

• This article was amended on 14 October 2010. We originally referred to Andrew Boff as Andrew Ruff. This has now been fixed.